KIT and gastrointestinal stromal tumor: DNA sequencing of the duodenal GIST identified a new 21 codon in frame deletion c1718:1739del21 (p.T574_H580delTQLPYDH) encompassing the internal part of the juxtamembrane zipper region of KIT (JM-Z, 10 amino acids, residues 572–581), an area adjacent to the first trans-phosphorylation sites (Tyr 568 and Tyr 570) (see Supplementary Figure 2).